In July 1965, Lyndon Johnson committed the United States to the ground war in Vietnam. This thesis argues that the 1965 decision marks a turning point in American foreign policy by creating a near Machiavellian Moment for the United States characterised by the question of Republic or Empire? To understand how the near-Machiavellian Moment changed American foreign policy, this thesis compares and contrasts Dean Rusk and Henry Kissinger. They will be compared and contrasted by asking three general questions. How did they view the United States? How did they view the World? How did they view the United States' role in the world? Dean Rusk represents a pre-Machiavellian Moment figure. His foreign policy philosophy of liberal internationalism reflects a belief in America's exceptionalism. Rusk justified the war by arguing that the United States' commitment to a decent world order was under threat in South Vietnam. Lyndon Johnson represents the Machiavellian Moment figure. He was caught between the international system, the commitment to a decent world order, and the domestic sphere, a commitment to deliver America's promise to all citizens. To overcome the dilemma, Johnson attempted to wage war and carry out reforms simultaneously. The decision created an imbalance at the heart of the Republic. The imbalance within the American regime and between the American regime and the international system brought the United States to the brink of Empire. Henry Kissinger represents a post-Machiavellian Moment figure. He rejected Rusk's foreign policy universalism. For him, the United States is a "normal" country that pursues a limited foreign policy based upon realpolitik. Rather than seeking to reform the international system, Kissinger sought to manage it. The thesis concludes that Rusk and Kissinger and their foreign policy alternatives represent the inherent tension between the American regime and the international system it supports.